How does the heart pump blood around the body?

The easiest way to think of the human heart is as 2 separate pumps in one loop. The first pump is the right side of the heart, which receives deoxygenated blood from the systemic circulation (the body). This blood first comes into the right atrium from either the superior vena cava (head and arms) or inferior vena cava (trunk and legs). The blood is then pumped from the right atrium to the right ventricle before leaving the heart through the pulmonary trunk, which splits into the left and right pulmonary arteries. Pulmonary arteries then enter the lungs and divide into capillaries where the blood becomes oxygenated, picking up oxygen and dropping off CO2 by gas exchange. The capillaries then rejoin to become pulmonary veins, as they leave the lungs and re-enter the heart at the left atrium. The now oxygenated blood is then pumped from the left atrium to the left ventricle before leaving the heart in the aorta, where it is delivered to the body tissues in capillaries witch eventually rejoin to form the superior or inferior vena cava.